Process and apparatus for producing light hydrocarbons



H. BUTLER PROCESS AND APPARATUS FOR PRODUCING LIGHT HYDROCARBONS FiledDec. 27, 1926 vwwtoz aMozM-Q h W Patented Aug. 4, 1931 UNITED STATESPATENT OFFICE HORACE BUTLER, OF WEST CHESTER, PENNSYLVANIA, ASSIGNOR TORESEARCH PROCESS COMPANY, A CORPORATION OF DELAWAR PROCESS AND APPARATUSFOR PRODUCING LIGHT HYDROGARBONS Application filed December 27, 1926.Serial No. 157,014.

My invention relates to apparatus and a process for producing lighthydrocarbons and particularly light hydrocarbons of which gasoline iscomposed.

It has been proposed to produce gasoline by the so-called cracking ofheavier hydrocarbons of crude petroleum but many'difficulties areencountered in the practice of such a process including the formation ofcarbon deposit in the still in which the cracking operation is carriedon. Furthermore, it has not been found commercially possible heretoforeto convert into gasoline hydrocarbons all of such petroleum or petroleumproducts as are introduced into the cracking still.

It has also been proposed to produce gasoline from natural gas by theso-called absorption methods in which certain constituents of thenatural gas are absorbed in a medium 2o contacted with the natural gasand then distilled off of such medium and then liquefied in whole or inpart by compression and cooling. In such absorption processes, however,only a small part of the natural gas is converted into gasoline of areadily usable form and even a large part of those hydrocarbons presentin the natural gas and desi-rable as gasoline constituents, is notbrought into the gasoline so produced. 4

Moreover, the production of gasoline by mixing light hydrocarbons suchas natural gas with vaporsproduced by distillation of crude petroleum isimpracticable because ex- 4 tremely high pressures would be necessary toeffect stable liquefaction to a reasonable extent ofthe resultingmixture of vapors and gases. V It is an object of myinvention to provideapparatus and a process whereby the difli- 40 culties and disadvantagesof previously known processes for the production of gasoline will besubstantially avoided.

In the practice of my invention a charging material consisting of crudepetroleum or fractions, residues or products thereof,

that include .hydrocarbons that possess boil.

ing points so high that they are not suitable as constituents ofgasoline, is subjected to cracking in a cracking zone, in liquid phaseor in vapor phase or in both phases successively, and hydrocarbons ofsuitably low boiling point are utilized in connection with the crackingoperation, preferably by being introduced separately or together withother substances into the cracking zone or into the vapors thereof or inpart into the cracking zone and in part into the vapors thereof, andthen the resulting vapors are condensed. In such an operation the addedhydrocarbons of suitably low boiling point preferably possess aresultant condensation pressure or average partial pressure as low as iscompatible with the production, without change of conditions in thecracking zone, of a final product of desired initial and end points andsufficiently low to permit a reasonably complete combination and stableliquefaction of. the vapors coming from the cracking zone by the use ofpressure low enough to be readily produced in the commercial productionof gasoline.

My invention contemplates the utilization of such suitably low boilinghydrocarbons of suitably low average partial pressure in connection withboth liquid phase cracking and vapor phase cracking (independently orsuccessively employed upon the same material) of relatively high boilingpetroleum products; and it contemplates also the use of steam in thecracking operations.

Natural gas contains hydrocarbons which as originally constituted aresuitable as constituents of commercial gasoline, but it also contains inlarge quantities constituents, such-as methane, of which the partialpressure is so high that'combination and stable liquefaction of theconstituents of a mixture of vapors coming from a cracking operation towhich natural gas has been added, cannot be obtained to a reasonableextent by the employment of known methods. In other words theutilization of natural gas in connection with the cracking ofpetroleumprod uctsin an effort to produce gasoline gives rise to a vapor mixtureof such high resultant or average partial pressure that liquefactionthereof to" a reasonable extent cannot be effected by known means. 1Accordingly, a specific application of my invention resides in utilizingin connection with the cracking of petroleum products in the productionof possess high partial pressure.

' lectivelv withdrawn from thenatural gas.

gasoline, natural gas which has been so treated as to reduce itsresultant or average pressure as by elimination from the natural .gas ofconstituents, such as methane, that Such reduction of the resultant oraverage pressure of natural gas may be effected in the practice of myinvention by contacting the natural gas with an absorbent medium, suchas mineral seal oil, and thereby absorbing constituents of relativelylower partial pressure and then distillin from the absorbent medium, thehydrocar ons so absorbed thereby and thus producing as the vapors ofsucha still, a mixture of hydrocarbon vapors having a lower resultant oraverage liquefaction pressure than that of natural gas treated, it be-'ing well known that in such an absorption operationthe hydrocarbons ofhigher parpletely absorbed by the absorption medium. Thus, suitablelow-boiling hydrocarbons are selected from the natural gas used.

In the practice of this specific application of my invention all or somedesired fraction of the hydrocarbons distilled from the absorbent mediumthat has previously'been contacted with natural gas may be introduceddirectly into the cracking zone or into directly into the crackin zoneand another part into the vapors thereof, so long as enough of suchlight hydrocarbons enter the cracking zone to eliminate the deposit ofcarbon therein. In such an operation it may be advisable for mechanicalreasons to subject the vapors distilled from the absorbent medium tocompression or to cooling or to both of'such operations, in known manneror as herein described, to reduce such vapors to a liquid state or inpart to a liquid state and 1n part to a vapor state. If such vapors arereduced to a liquid state only in part then the uncondensed vapors alonemay be utilized in connection with the cracking of petroleumproductsorthe resultant liquid hydrocarbons of low boiling point may be soutilized, or both such liquid and such va ors may be so utilized. Thus,any desired raction may be used of the hydrocarbons so se- In thepractice of my invention the vapors produced by the utilization of lighthydrocarbons in connection with the cracking of petroleum products maybe subjected to cooling to produce a final liquid product or such finalliquid product may be produced by the application of other more or lesseffective steps, such as the application of pressure, with or withoutthe addition of further heat, the vapors being finally cooled. Atnydesired precautions may be taken in weathering (elimination of verylight h drocarbons without loss of desired hydrocarbons) of the Y finalproduct.

tial pressure, such as methane, are not comvapors thereof or a part maybe introduced I have found that in the practice of my invention noobjectionable deposit of carbon occurs in the cracking zone andsubstantially all of the petroleum products introduced into the crackingchamber are converted into gasoline hydrocarbons, even though thelighter hydrocarbons,utilized in connection with the cracking operationby being introduced directly into the cracking zone consist only ofuncondensed vapors remaining after the vapors of an absorption-mediumstill are subjected to compression and cooling to produce liquidgasoline from the constituents of natural gas which had been absorbed inthe absorption-medium. Merely cooling the vapors resulting from theaddition of uncondensed absorption-still vapors to the cracking zoneproduced commercial motor fuel in a quantity greater than that of thepetroleum products introduced into the cracking chamber.

In the practice of my invention uncondensed vapors of theabsorption-still or uncondensed vapors coming from the crackingoperation or both may be advantageously recirculated in the system bybeing reintroduced into the operations in which hydrocarbons fromnatural gas are being treated or by being introduced into the crackingzone.

When the light hydrocarbons utilized-in connection with the crackingoperation are derived from natural gas as above described the operationswhereby gasoline hydrocarbons are obtained from natural gas ,and theoperations whereby light hydrocarbons are utilized in connection withcracking, so coduction being substantially free of diflicultiesencountered in the production of gasoline from either of those sources.My invention, therefore, comprises not only the step of utilizing, inconnection with the cracking of petroleum products to produce gasoline,light hydrocarbons of sufliciently low resultant or average pressure topermit reasonably complete and stable combination and liquefaction ofthe resultant vapors, but also the production of gasoline from naturalgas and the cracking of petroleum products in such cooperative relationthat the resultant vapors are susceptible of combination and stableliquefaction to a practical extent without use of excessive pressures.

In the drawing'there is shown diagrammatically one form of apparatusembodying my invention and whereby my invention may be practised but itis to be understood that myv invention is not limited to such embodimentwhich is intended to be merely exemplary and which is described only forthe the absorbent medium the hydrocarbons so absorbed and for thencompressing the hydrocarbon vapors-so evolved, means for utilizing inconnection with the cracking of petroleum products all or some part ofthe vapors evolved from the absorption-mediumstill, means for obtainingliquid gasoline from the vapors coming from the cracking operation andmeans for recirculating uncondensed yapors.

' The absorber 1 may be of any desired construct-ion but should be sodesigned as to be highly eflicient, preferably efl'ecting an absorptionof as much of the natural gas as possible with the exception ofhydrocarbons thereof having very high partial pressures, such asmethane. The natural gas is led into the absorber 1 through the inlet 2and absorption medium, such as mineral seal oil, is led into theabsorber by the inlet 3, the unabsorbed gas passing out of the absorberthrough the pipe 4, and oil containing absorbed hydrocarbons passingfrom the absorber 1 through the pipe 5. The absorber 1 is advantageouslyoperated as in known natural gas absorption systems or various featuresof operation maybe carriedon as described in the copending applicationfiled August 7th,'-1926, by myself and Alexander Clarke, Ser. No.127,718.

The oil containing absorbed hydrocarbons passes through pipe 5 into venttank 6, which is provided with a vent 6, and then is passed by pump 7through heat exchanger 8 and heater 9 into a still 10 which may resemblea fractionating tower and may be of the standard bell and washer type.,Inthe still 10 some of the absorbed hydrocarbons are liberated from theabsorption medium and it then passes through pipe 11 into steam still 12which may resemble a fractionating tower in construction. From the steamstill 12 the oil is passed through pipe 13 by means of pump 14 to theheat exchanger 8 and then to cooling coils 15 and through arefrigerating device 16 from which the oil passes to inlet 3 ofabsorber'l. The use ofthe refrigerating device 16 is optional and it mayonly be necessary torefrigerate some part of the stripped absorptionmedium, for. example, the part entering the upper zone of the absorber1.

Absorption 'medium containing absorbed hydrocarbons is heated in heater9 to a temperature approaching the initial boiling point of theabsorption medium, for example,

400 F. to 500 F. Steam is supplied to steam' still 12 by boiler 65, thesteam preferab l.

. passing'through superheater 66 and pipe 6 to still 12.

Light hydrocarbon vapors liberated in still 10 pass through pipe 17 toknockout 18 in I which suitable reduction of temperature eliminatesundesirable fractions including lighter parts of the absorption medium,resulting liquid returning to still 10 through pipe 19. Vapors fromknockout 18 pass through pipe 20 to compressor 21 where the pressure ofthe vapors is increased to about 40 pounds per square inch, pressuresreferred to herein being gauge-pressures. The cornpressed vapors passthrough cooler 22 and the resultant vapors and'liquids are collected inaccumulator 23.

Vapors evolved in steam still 12 pass through pipe 24 to knockout 25from which any collected liquid is returned to still 12 through pipe25'. Vapors pass from knock out 25 through cooling coil 26 into aseparating tank 27 from which Water is drained by cock 28 and from whichvapors pass through pipe 29 to outlet 17 of still 10, and from whichliquid hydrocarbons are passed by pump 30 to accumulator tank 23.

The hydrocarbons collected in liquid and vapor form in accumulator tank23 Will possess a resultant or average partial pressure a considerablylower than that of the natural gas from which said collectedhydrocarbons are derived.

Uncondensed vapors in accumulator tank 23 pass to compressor 31 wheretheir pres-. sure is increased to 225 to 250 pounds. The hydrocarbonvapors pass from compressor 31 through pipe 32 to cooler 33 and theresult-ing liquid and uncondensed vapors are collected in high stageaccumulator tank 34.

With a View to improving the operation of the apparatus so far describedfor the ab- ,sorption and distillation of the light hydrocarbons derivedfrom natural gas a part of the'uncondensed vapors in the high stageaccumulator tank 34 may be carried through pipe 35 to heater 36 andintroduced into the light hydrocarbonabsorption system at some pointpreceding the condensation of the absorbed light hydrocarbons, forexample, .by

means of pipe 37 leading from heater 36 into still 10.

Cracking chamber 50 of any suitable form and suitably operated issupplied with crude petroleum or products thereof from tank 51,

the charging material in tank 51 being passed by pump 52 into feed tank53 where the desired pressure, 225 pounds per square inch or higher, ismaintained. The charging material passes from feed tank 53 through pipe54 and through heater 55 into the upper part of cracking chamber 50through pipe 56, and any charging material drained from chamber 50through pipe 57 is returned by pump 58 through pipe 59 to the inflawingcharging material in pipe 56. Cracking chamber 50 may be provided with asupplementalheater The charging material may be heated in heater tosuitable temperatures, for example, temperatures up to 1000 F. and thepressures maintained will depend upon the temperature employed, thedesign of the heater, rate of flow, etc.

Light hydrocarbons of suitable average or resultant pressure areintroduced into crackmay be passed into pipe 63 leading to heater 62 byopening val-ve a in pipe 64, closing valve 1) in pipe 32 and openingvalve 0 in pipe 65. By opening valve 66, liquid in low stage accumulatortank 23 may be passed by pump 67 into pipe 68 that leads to pipe thatopens into pipe 63. Liquid in high stage accumulator tank 34 may be alsopassed into pipe 68 by opening valve d. Accumulator tanks 23 and 34 arerespectively provided with drain cocks 69 and 70 in the event that theliquid hydrocarbons therein are to be withdrawn for immediate use or inorder to be stabilized and so converted from wild gasoline intocommercial gasoline.

The upper zone of the cracking chamber 50 may be of the bell and washertype of scrubber or fractionating column as indicated diagrammaticallyor the vapors from the cracking zone may be passed through pipe 71 toknockout 72 Where undesirable fractions are eliminated, by reduction oftemperature if necessary, "and returned to the cracking chamber throughpipe 73. Vapors from knockout 72 pass through pipe 74 and are condensed.Such condensation may be effected directly by cooler 75 and the resultinliquids and vapors are collected in tank 6 from which they may beithdrawn to storage with or without being subjected to stabilization. Byclosing valve 6 in pipe 74 and opening valve f, the resultant vapors maybe sub-' jected to compression and heat prior to their introduction intothe cooler 75. To this end the vapors may be cooled for mechanicalreasons in cooler 77 and compressed by compressor 78 until the pressureis sufficiently increased even up to 1000 pounds. Liquid formed upon thecooling of the vapors in cooler 77 is collected in trap 7 9 and returnedby pump 80 to the vapors discharged from compressor 78. The productsthen pass through heater 81 in which the temperature may be raised toany desired point even to 1000 F. and are then passed to cooler 75.

Such light hydrocarbons as are introduced into pipe 68 may be passedinto the vapors coming from the cracking still by closing c5 valve 0 andopening valve g in pipe 82 that ing valve 7' in pipe 84 or they may berecirculated in the cracking operation by passing them into the crackingchamber through pipe 85 or through the pipe 86 into the vapors comingfrom the cracking chamber, pump 87 being provided for that purpose.

Light hydrocarbons derived from natural gas and utilized in the'practiceof my invention contain some air of which the oxygen by combination withhydrocarbons is converted into steam which may assist the phenomenaoccurring in the practice of my invention; and if, under the conditionsof op-' eration, which will obviously vary greatly,

the use of additional steam is helpful it may be employed as by passingsteam through the superheater 88 and conducting it through pipe 89 intothe chamber 50.

Many valves and control devices in addition to the valves that have beenreferred to,

some of which additional valves are indicated, may be" employedforregulating the flow of'liquids and vapors in the practice of myinvention, particularly to the end that either uncondensed vapors fromaccumulator tank 34 or liquids from accumulator tank 23, or liquids fromaccumulator tank 34, or any one or moreof those fractions of the vaporsdistilled from the absorption medium, may be introduced into the chamber50, or into the pipe 74, or in part into one and in part into theother.

The increase of pressure created by compressor 78 and the temperature atwhich the compressed gases are maintained by heater 81 may be such thatthat temperature and that pressure will merely'assist in condensation incooperation with cooler 75, or they may be made sufliciently hightocause cracking, polymerization and combination which are additional orsupplementary to any similar efiects produced in the chamber 50, or whensuch high temperatures and pressures are produced by compressor 78 andheater 81, the chamber 50 may be operated at lower temperatures, even attemperatures which will merely efi'ect distillation.

From the foregoing it will be apparent that I have provided apparatusand a process whereby light hydrocarbons of suitably low resultant oraverage pressure, for example, suitable v hydrocarbons selectivelyderived from natural gas, may be utilized in connection with thecracking of petroleum products to produce gasoline and wherebyproduction of gasoline from natural gas, and production of gasoline fromheavier petroleum products are carried on in such cooperation thatgasobe carried line is economically produced with substantial avoidanceof the difficulties encountered in production of gasoline by absorptionor by cracking when those methods of production are separately used, andwhereby cracking of relatively heavy petroleum products in liquid phaseor apor phase and cracking of lighter hydrocarbons in vapor phase andcombination or polymerization in such manner as to produce gasoline ofdesired characteristics, are so carried out as to avoid difiicultiesheretofore encountered in such operations.

While I have described in great detail features of apparatus and of theoperations thereof whereby my invention may be practiced I do not intendthat my invention shall be limited thereto but intend that'it shallinclude such modifications and variations as fall within the appendedclaims. In this connection .I would point out that the operations ofabsorbing hydrocarbons from natural gas and distilling them from theabsorptionmedium and the treatment of such still vapors includingrecirculation thereof, may

scribed in the above-mentioned application filed by myself and AleXanderClarke. Thus, in that treatment of those still vapors the pressures andtemperatures may be varied and increased to effect such cracking andcombination or polymerization thereof as may be desirable in theproduction and condensation of desired hydrocarbons from absorbedconstituents of natural gas. Fur thermore, the temperatures andpressures in the cracking operations herein described and in anyrecompression and reheating of the vapors therefrom may be varied 'andincreased to bring about production of desired hydrocarbons in thecracking zone or in the vapors coming therefrom.

YVhat I claim as new and desire to secure by Letters Patent of theUnited States is:

1. In the production of gasoline the process comprising withdrawinglight hydrocarbons from natural gas by-absorption, compressing andcooling said hydrocarbons, introducing uncondensed vapors of saidcooling operation into a zone wherein petroleum products are beingcracked in liquid phase, and cooling the vapors coming from the crackingoperation.

2. In the production of gasoline the process comprising absorbing lighthydrocarbons from natural gas by an absorption medium, distilling theabsorbed hydrocarbons from said medium, compressing and cooling thestill vapors, recirculating uncondensed vaporsof said cooling operationinto said distilling and compressing and cooling operations, passingremaining products of said distilling operation into a zone whereinpetroleum products are being cracked in liquid phase, and cooling theresulting vapors.

out by the steps and features deline comprising .means for distillingabsorbed hydrocarbons pressing and cooling means,

-3. In the production of gasoline the process comprising absorbing lighthydrocarbons from natural gas by an absorption medium, distilling thevabsorbed hydrocarbons from said medium, compressing and cooling thestill vapors, recirculating uncondensed vapors of said cooling operationinto said distilling andcompressing and cooling operations, passingremainingproducts of said distilling operation into a zone whereinpetroleum products are being cracked in liquid phase, cooling theresulting vapors, and recirculating to said cracking zone uncondensedvapors of said last named cooling operation.

4. In the production of gasoline the process comprising absorbing lighthydrocarbons from natural gas by an absorption medium, distilling theabsorbed hydrocarbons from said medium, compressing and cooling thestill vapors, recirculating uncondensed vapors of said cooling operationinto said distilling and compressing and cooling operations, passingremaining products of said distilling operation into a zone whereinpetroleum products are being cracked in liquid phase, further heatingand compress ing the vapors coming from said cracking zone, and coolingsaid heated and compressed vapors.

5. In the production of gasoline the process comprising absorbing lighthydrocarbons from natural gas by an absorption medium, distilling theabsorbed hydrocarbons from said medium, compressing and cooling thestill vapors, recirculating uncondensed vapors of said cooling operationinto said distilling and compressing and cooling operations. passingremaining products of said distilling operation into a zone whereinpetroleum products are being cracked in liquid phase, and furthercompressing and then cooling the vapors coming from said cracking zone.

6. Apparatus for the production of gasoan absorber for natural gas ofthe natural gas from the absorbing medium of said absorber, means forcompressing and cooling vapors of said still, means for recirculating tosaid distilling and comuncondensed vapors from said compressing andcooling means, a cracking chamber for petroleum products, means forintroducing into said cracking chamber remaining hydrocarbons from saidcompressing and cooling means, means for cooling the vapors of saidcracking chamber and means for recirculating to said cracking chamberuncondensed vapors of said last named cooling means.

In testimony whereof, I have signed my name to this specification.

HORACE BUTLER.

